(1) Field of the Invention
The present invention belongs to a technical field of a playback technology for 3D video and 2D video.
The present invention relates a playback technology for stereoscopic video, and in particular, to the allocation of video data on a recording medium.
(2) Description of the Related Art
In recent years, along with an increase in the number of 3D movie works, there is an increasing demand for storing 3D video in optical discs while maintaining the 3D video at high image quality, in order to supply these movie works for home use.
When storing 3D video on an optical disc, the disc requires playback compatibility with a playback device that can playback only an optical disc having stored 2D video (hereinafter, referred to as “2D playback device”). If the 2D playback device cannot play back the 3D video stored on the optical disc, as 2D video, the same contents need to be manufactured in two types of discs, i.e. 3D discs and 2D discs, leading to a cost increase. Accordingly, it is preferable that the optical disc having stored the 3D video can be played back as 2D video by a 2D playback device and as 3D video by a playback device that can playback both 2D video and 3D video (hereinafter, “2D/3D playback device”). Also, with use of an optical disc having the playback compatibility, it is possible to enjoy both 3D video and 2D video with a 2D/3D playback device.
FIG. 104 is a schematic diagram illustrating the technology for ensuring the compatibility of an optical disc storing 3D video content with 2D playback devices (see Patent Literature 1). An optical disc 6701 stores two types of video stream files. One is a 2D/left-view video stream file, and the other is a right-view video stream file. A “2D/left-view video stream” represents a 2D video image to be shown to the left eye of a viewer during 3D playback, i.e. a “left-view”. During 2D playback, this stream constitutes the 2D video image. A “right-view video stream” represents a 2D video image to be shown to the right eye of a viewer during 3D playback, i.e. a “right-view”. The left and right video streams have the same frame rate but different presentation times shifted from each other by half a frame period. For example, when the frame rate of each video stream is 24 frames per second, the frames of the 2/D left-view video stream and the right-view video stream are alternately displayed every 1/48 seconds.
As shown in FIG. 104, the left-view and right-view video streams are divided into a plurality of extents 6702A-C and 6703A-C respectively on the optical disc 6701. Each extent contains at least one group of pictures (GOP), GOPs being read together from the optical disc. Hereinafter, the extents belonging to the 2D/left-view video stream are referred to as “2D/left-view extents”, and the extents belonging to the right-view video stream are referred to as “right-view extents”. The 2D/left-view extents 6702A-C and the right-view extents 6703A-C are alternately arranged on a track 6701A of the optical disc 6701. Each two adjacent extents 6702A-6703A, 6702B-6703B, and 6702C-6703C have the same length of playback time. Such an arrangement of extents is referred to as an interleaved arrangement. A group of extents recorded in an interleaved arrangement on a recording medium is used both in 3D video playback and 2D video image playback, as described below.
From among the extents recorded on the optical disc 6701, a 2D playback device 6704 causes an optical disc drive 6704A to read only the 2D/left-view extents 6702A-C sequentially from the start, skipping the reading of right-view extents 6703A-C. Furthermore, an image decoder 6704B sequentially decodes the extents read by the optical disc drive 6704A into a video frame 6706L. In this way, a display device 6707 only displays left-views, and viewers can watch normal 2D video images.
A 3D playback device 6705 causes an optical disc drive 6705A to alternately read 2D/left-view extents and right-view extents from the optical disc 6701. When expressed as codes, the extents are read in the order 6702A, 6703A, 6702B, 6703B, 6702C, and 6703C. Furthermore, from among the read extents, those belonging to the 2D/left-view video stream are supplied to a left video decoder 6705L, whereas those belonging to the right-view video stream are supplied to a right-video decoder 6705R. The video decoders 6705L and 6705R alternately decode each video stream into video frames 6706L and 6706R, respectively. As a result, left-views and right-views are alternately displayed on a display device 6708. In synchronization with the switching of the views by the display device 6708, shutter glasses 6709 cause the left and right lenses to become opaque alternately. Therefore, a viewer wearing the shutter glasses 6709 sees the views displayed by the display device 6708 as 3D video images.
When 3D video content is stored on any recording medium, not only on an optical disc, the above-described interleaved arrangement of extents is used. In this way, the recording medium can be used both for playback of 2D video images and 3D video images.